close of the century, did much to establish conceptions of the
universe and its laws upon a scientific basis." And not only did
Rousseau make botany fashionable, but Goldsmith wrote from Paris in
1755: "I have seen as bright a circle of beauty at the chemical lectures
of Rouelle as gracing the court of Versailles." Petit lectured on
astronomy to crowded houses, and among his listeners were gentlemen and
ladies of fashion, as well as professional students.[68] The
popularizers of science during this period were Voltaire, Montesquieu,
Alembert, Diderot, and other encyclopaedists.

Here should be mentioned one of Buffon's contemporaries and countrymen;
one who was the first true field geologist, an observer rather than a
compiler or theorist. This was Jean E. Guettard (1715-1786). He
published, says Sir Archibald Geikie, in his valuable work, _The
Founders of Geology_, about two hundred papers on a wide range of
scientific subjects, besides half a dozen quarto volumes of his
observations, together with many excellent plates. Geikie also states
that he is undoubtedly entitled to rank among the first great pioneers
of modern geology. He was the first (1751) to make a geological map of
northern France, and roughly traced the limits of his three bands or
formations from France across the southeastern English counties. In his
work on "The degradation of mountains effected in our time by heavy
rains, rivers, and the sea,"[69] he states that the sea is the most
potent destroyer of the land, and that the material thus removed is
deposited either on the land or along the shores of the sea. He thought
that the levels of the valleys are at present being raised, owing to the
deposit of detritus in them. He points out that the deposits laid down
by the ocean do not extend far out to sea, "that consequently the
elevations of new mountains in the sea, by the deposition of sediment,
is a process very difficult to conceive; that the transport of the
sediment as far as the equator is not less improbable; and that still
more difficult to accept is the suggestion that the sediment from our
continent is carried into the seas of the New World. In short, we are
still very little advanced towards the theory of the earth as it now
exists." Guettard was the first to discover the volcanoes of Auvergne,
but he was "hopelessly wrong" in regard to the origin of basalt,
forestalling Werner in his mistakes as to its aqueous origin. He was
thus the first